DHNA has been known to be useful for industrial materials as dyes, pigments or photographic sensitive materials, and heretofore various synthetic methods by organic chemical synthesis have been developed. As a result of extensive studies by the inventors of the present invention on alternative method for production of DHNA, they have found that a large amount of DHNA could be produced by propionic acid bacteria in or outside the cell and they have found that a composition containing DHNA, or 1,4-dihydroxy-2-naphthoic acid or a salt thereof isolated from the culture had an action for reducing abdominal discomfort caused by lactose intolerance observed at the time of ingestion of milk and at the same time it was useful for prevention and treatment of metabolic bone disease (Patent document 1).
Although according to such a method, it has become possible to use DHNA for beverages and pharmaceutical products, the composition containing DHNA is not always satisfactory in terms of flavor and as a result it has been difficult to use it frequently for commercial products.
[Patent document 1]: WO 03/016544